Flat flame burner having a low air to gas ratio

ABSTRACT

A flat flame burner capable of sustaining combustion at a low air to gas ratio. The burner has a cup shaped combustion chamber with outwardly extending tapered walls leading from the combustion chamber. At the upstream end of the combustion chamber, generally tangential means is provided for introducing a mixture of gas into the combustion chamber. The geometry of the burner is such that virtually total reaction takes place within the combustion chamber and along the tapered walls.

United States Patent [1 1 Nesbitt et a1.

[ 1 Jan. 1,1974

[ FLAT FLAME BURNER HAVING A LOW AIR T0 GAS RATIO [75] Inventors: JohnD. Nesbitt, Chicago, 111.; Klaus II. Hemsath, Sylvania, Ohio; Frank J.Vereecke, Palmyra, Mich.

[73] Assignee: Midland-Ross Corporation,

Cleveland, Ohio 22 Filed: Apr. 20, 1972 211 Appl. No.: 245,932

[52] US. Cl 431/185, 431/348, 239/399 [51] Int. Cl. F23m 9/00 [58] Fieldof Search 431/348, 173, 185,

[56] References Cited UNITED STATES PATENTS 1,656.907 1/1928 Bansen431/185 3.315.726 4/1967 Williams 431/348 2,890,746 6/1959 Dollinger431/173 3,286,997 11/1966 Lcdbetter 239/399 2,969,833 1/1961 Bloom eta1. 431/348 3,221,797 12/1965 Wall 431/348 2,941,585 6/1960 Loebel et a1431/174 Primary ExaminerCarroll B. Dority, Jr. Attorney-Peter Vrahotes[57] ABSTRACT A flat flame burner capable of sustaining combustion at alow air to gas ratio. The burner has a cup shaped combustion chamberwith outwardly extending tapered walls leading from the combustionchamber. At the upstream end of the combustion chamber, generallytangential means is provided for introducing a mixture of gas into thecombustion chamber. The geometry of the burner is such that virtuallytotal reaction takes place within the combustion chamber and along thetapered walls.

12 Claims, 3 Drawing Figures FLAT FLAME BURNER HAVING A LOW AIR TO GASRATIO BACKGROUND OF THE INVENTION With the greater demands placed uponthe heat treating industry, it is becoming desirable to have a burnerwhich will not only convey heat to work, but do it in such a manner thatthe work is provided with a protective atmosphere. This may be achievedby a burner which conveys heat generally radiantly, as opposed toimmediately exposing the work to the products of combustion, and tosubsequently provide a protective atmosphere to the heat treating area.This particular need is generally satisfied by a flat flame burner whichis able to operate at low air to fuel ratios. Such burners are availableon the market today, however, those presently available have certainshortcomings.

The primary shortcoming of the present day burners is that they areunable to accomplish complete combustion within the burner itself andmuch of the gas mixture leaves the area of the burner and completescombustion at a location away from it. This has certain disadvantages,as much of the heat is lost to the surface of the burner which wouldnormally transfer the heat radiantly, and combustion in the area of thework tends to promote oxidation since there is a portion of unreactedair. In addition to this, it is difficult to obtain a burner which notonly satisfies the requirements of low air to fuel ratio, but also has alarge tumdown ratio and the stability that is required for a largeturndown ratio.

It is therefore an object of this invention to provide a unique flatflame burner.

It is another object of this invention to provide a flat flame burnerwith high stability.

It is s till another object of this invention to provide a flat flameburner in which substantially complete combustion takes place within theburner.

It is a further object of this invention to provide a flat flame burnerhaving a high tumdown ratio.

These and further objects will appear from the following portion of thespecification and drawing, wherein:

FIG. 1 is a vertical cross-sectional view of a burner incorporating theprinciples of the invention taken along line 11 of FIG. 2;

FIG. 2 is a horizontal cross-sectional view taken along line 2-2 of FIG.1; and

FIG. 3 is a plan view of the bumer shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, aburner is shown generally at secured to the top of a furnace l2 andhaving a portion received within an opening 14 of the furnace. Theburner comprises a housing 16 which has a metallic shell 18 thatreceives refractory block 20. The refractory block 20 has a cup shapedcombustion chamber 22 which is confluent with the interior of thefurnace. An annular plate 24 is disposed about the housing 16 andsecures the housing to the furnace by the use of bolts 26 receivedwithin an annular plate 28 welded to the top of the furnace 12. Theportion of the burner 10 received within the opening 14 has a tapered,generally conical member 30 with a right cylindrical portion 32 whosediameter is somewhat larger than the diameter of the cup shapedcombustion chamber 22, thereby defining a transverse shoulder 34therebetween. The ratio of the length of the right cylindrical portion32 to its diameter should be 1/5 to H2, the preferred ratio beingapproximately U4. The ratio of the cylindrical 32 diameter to thechamber 22 diameter should be between 2/1 and 6/5. The conical member 30has tapered walls 36 that provide a smooth and regular surface from theupstream end of the conical member to the furnace 12 interior.

The upstream end of the combustion chamber 22 has a pair of dualdiameter ports 38 or openings. Each of the ports 38 has a large diameterportion 42 upstream from the chamber 22 and a small diameter portion 44adjacent to the chamber. Received within each large diameter portion 42of these ports 38 is one end of a sleeve 40. Each sleeve 40 has a firstopening 46 at the outermost end thereof of which receives a coaxiallydisposed gas line 48 that has a portion which extends a dis tance intothe ports 38 and an external portion which may be connected to a sourceof combustible gas. The interior end of the gas line 48 within thesleeve 40 is supplied with a spud 50 which has a small opening 52therein. Each sleeve 40 also has an opening 54 located at the upper endthereof, which opening receives an air manifold 56. The air manifold inturn is connected to an air supply line 58. Received within the housing16 and directed to the combustion chamber 22 is a pilot 60.

The ports 38 are generally tangentially disposed to the combustionchamber 22 as can be seen in FIG. 2. The ports 38 are not exactlytangential, but are offset by 24 so that the gases are directed slightlyaway from the wall of the combustion chamber 22. It has been found thathaving this slight angle to the tangential promotes mixing and stabilitywithin the combustion chamber 22. In a burner of the type to which thisinvention is directed, it is advantageous to promote mixing to achievemaximum combustion intensity. It has been found that particularrelationships between the small diameter portion 44 of the ports 38 andthe large diameter portion 42 aid in the primary mixing of the air andgas. Specifiallly, it has been found that if the diameter of the largeportion 42 is approximately twice that of the smaller portion 44, bettermixing is achieved, and a back pressure is obtained. Additionally, therelative lengths of the port portions 42 and 44 are important, and thelength of the larger diameter portion 42 should be approximately twicethe length of the smaller diameter portin 44. It also has been foundthat if the length from the spud. opening 52 to the necked down portionsof the ports 38, which length is indicated by a, is approximately 5 to10 times as great as the diameter of the spud opening 52, mixing ispromoted. Preferably, this difference is approximately 7.5.Additionally, this also aids in creating a back pressure required foroperation of the burning.

After the gases have been supplied to thecombustion chamber 22 andignited therein, further ixing is achieved by the pressure of theshoulder 34. Once the gases have reached the end of the cone shapedsection of member 30, the gas mixture is virtually completely reacted,transferring heat to the tapered walls 36 which act as radiatingmembers.

The burner 10 has a high stability when used with either cold orpreheated air. In a test run of the burner 10, no instability was notedin operation with l,000 F. preheated air at air/gas ratios ranging from10/ l to 5/1. The burner was also found operational at air to gas ratiosas low as 6.5/1 using cold air. At ratios below 6.5/1 using cold air thepresence of free carbon was found in the flue gas. Again using cold air,slight instability was detected at ratios above 17/1, but theinstability did not reach a point of flame blowout at /1.

What is claimed is:

1. A flat flame burner comprising: a housing, an opening within saidhousing defining a cup shaped combustion chamber, a pair of dualdiameter ports extending through the housing to the interior portion ofthe wall of said chamber in a generally tangential manner, a membersecured to the housing and having a generally conically-shaped interiorin a confluent relationship with said chamber, said member having itssmaller diameter end adjacent to and larger than the diameter of saidchamber to define a shoulder, each of said ports having a first portionadjacent said chamber and a second portion adjacent and upstream of saidfirst portion, said second portion having a larger diameter than saidfirst portion, and means for supplying combustion gas and air to saidports in a coaxial direction.

2. The burner of claim 1 wherein each of said ports is positioned at a24 angle relative to the tangential of said chamber.

3. The burner of claim 1 wherein said second portion of each port has adiameter approximately twice as large as the diameter of said firstportion.

4. The burner of claim 3 wherein the length of said second portion istwice the length of said first portion.

5. A flat flame burner comprising: a housing, a cup shaped openingwithin said housing defining a chamber, a member secured to the housingand having a recessed interior in the form of a right cylindricalportion having tapered walls extending from said cylindrical portion,said cylindrical portion being adjacent said chamber, a plurality ofports extending through the housing into said chamber in a generallytangential manner each of said ports having a first portion adjacentsaid opening with a first diameter and a second portion adjacent andupstream of said first portion with a second diameter larger than saidfirst diameter, means for providing air and gas to said second portionof each of said ports in a coaxial direction.

6. The burner of claim 5 wherein the length of said second portion isapproximately twice as long as the length of said first portion.

7. The burner of claim 5 wherein said gas supply means is alongitudinally extending tube received within the second portion of saidport with the terminating end of said gas tube having an openingtherein.

8. The burner of claim 5 wherein the diameter of said right cylindricalportion is larger than the diameter of said cup shaped opening therebydefining a transverse shoulder.

9. The burner of claim 7 wherein the distance from where the tubeterminates within said second portion to the beginning of said firstportion is between 5 and 10 times greater than the diameter of saidopening in said tube.

10. The burner of claim 9 wherein said distance is 7.5 times greaterthan the diameter of said opening.

11. The burner of claim 5 wherein the diameter of said right cylindricalportion is 2/1 to 5/1 times greater than its length.

12. The burner of claim 8 wherein the diameter of said right cylindricalportion is 6/5 to 2/1 times greater than the diameter of said opening.

257533 UNHE'I) STATES PA ENT OFFICE") (TI id H" l" i H'*.?[ (2 AT E 0 FC U R R E (35H @N Patent Ne. 883 Dated January 1, 1974 Inventor) John D.Nesbitt, KleueH. item eath and Frank J. Vereecke:

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

1* W K' Abstr act, line 7, after "gas". insert rand air Column 2, line16, delete "o".- Line/Ll, change "specifia lll y" to specificallyLine48, ehange "portin" to portion Line 57 change "ixing"' to-Yf'imixing Line 58,achange "pressure" to---- presence Q? l Celurnn 4,line 23, ehange; e" to to Signed and sealed this 16th (18.15] of April19711 I (SEALY Attest EDWARD 1%.1 L3T0HE1J JR. n c; MMKSHALL DANNAttesting Officer. Commissionenof Patents

1. A flat flame burner comprising: a housing, an opening within saidhousing defining a cup shaped combustion chamber, a pair of dualdiameter ports extending through the housing to the interior portion ofthe wall of said chamber in a generally tangential manner, a membersecured to the housing and having a generally conically-shaped interiorin a confluent relationship with said chamber, said member having itssmaller diameter end adjacent to and larger than the diameter of saidchamber to define a shoulder, each of said ports having a first portionadjacent said chamber and a second portion adjacent and upstream of saidfirst portion, said second portion having a larger diameter than saidfirst portion, and means for supplying combustion gas and air to saidports in a coaxial direction.
 2. The burner of claim 1 wherein each ofsaid ports is positioned at a 2*-4* angle relative to the tangential ofsaid chamber.
 3. The burner of claim 1 wherein said second portion ofeach port has a diameter approximately twice as large as the diameter ofsaid first portion.
 4. The burner of claim 3 wherein the length of saidsecond portion is twice the length of said first portion.
 5. A flatflame burner comprising: a housing, a cup shaped opening within saidhousing defining a chamber, a member secured to the housing and having arecessed interior in the form of a right cylindrical portion havingtapered walls extending from said cylindrical portion, said cylindricalportion being adjacent said chamber, a plurality of ports extendingthrough the housing into said chamber in a generally tangential manner,each of said ports having a first portion adjacent said opening with afirst diameter and a second portion adjacent and upstream of said firstportion with a second diameter larger than said first diameter, meansfor providing air and gas to said second portion of each of said portsin a coaxial direction.
 6. The burner of claim 5 wherein the length ofsaid second portion is approximately twice as long as the length of saidfirst portion.
 7. The burner of claim 5 wherein said gas supply means isa longitudinally extending tube received within the second portion ofsaid port with the terminating end of said gas tube having an openingtherein.
 8. The burner of claim 5 wherein the diameter of said rightcylindrical portion is larger than the diameter of said cup shapedopening thereby defining a transverse shoulder.
 9. The burner of claim 7wherein the distance from where the tube terminates within said secondportion to the beginning of said first portion is between 5 to 10 timesgreater than the diameter of said opening in said tube.
 10. The burnerof claim 9 wherein said distance is 7.5 times greater than the diameterof said opening.
 11. The burner of claim 5 wherein the diameter of saidright cylindrical portion is 2/1 to 5/1 times greater than its length.12. The burner of claim 8 wherein the diameter of said right cylindricalportion is 6/5 to 2/1 times greater than the diameter of said opening.